Update pytest.yml

.github/workflows/pytest.yml

@@ -26,7 +26,7 @@ jobs:
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip
-        pip install flake8 pytest matplotlib cycler
+        pip install flake8 pytest matplotlib cycler seaborn
     - name: Lint with flake8
       run: |
         # stop the build if there are Python syntax errors or undefined names